Permanganate Titration

Principle

This method utilizes the reduction of potassium permanganate (KMnO4) by hydrogen peroxide in sulfuric acid.

Scope of Application

This method is suitable for measuring aqueous solutions of H2O2 ranging from 0.25 to 70 wt.%.

Interferences

Any substance which reduces KMnO4 under acidic conditions will produce a positive interference.

Safety Precautions

Please consult Safety and Handling guidelines (see here), particularly as relates to personal protective clothing and footware. Neoprene or PVC aprons are recommended, as are monogoggles and neoprene rubber gloves. Sample bottles containing H2O2 should not be stoppered, but rather vented or covered loosely with aluminum foil or paraffin film. Solutions withdrawn from a sample bottle should not be returned to that bottle but should be flushed down the drain with plenty of water. Any spills should be flushed with water immediately as should any combustible materials which should come into contact with H2O2. Do not use adsorbent media to clean up H2O2 spills.

Reagents

1. Concentrated sulfuric acid. Reagent Grade H2SO4 (sp.gr. 1.84).
2. Potassium permanganate (0.3N). Standardized against NIST sodium oxalate.

Procedure

1. From the table below, transfer an appropriate aliquot of H2O2 sample to a tared weighing bottle and weigh on an analytical balance.
   

   Expected H2O2 Concentration (wt.%)	Suggested Sample Amount (gms)
   0.25-1.0	100-250
   1-3	30-100
   3-10	10-30
   10-35	3-10
   35-70	1.5-3.0

2. Carefully wash the weighed sample into a 250-mL volumetric flask with distilled water, dilute to the mark and mix thoroughly.
3. Pipet a 25-mL aliquot into a 400 mL beaker containing 250-mL of distilled water and 10 mL of concentrated sulfuric acid.
4. Titrate to the first permanent pink color with 0.3N potassium permanganate.

Calculation

% H₂O₂ (by weight) = [(mLs KMnO₄) x (N) x (0.01701) x (1000)] / (grams of H₂O₂ sample used) where: N = Normality of the standardized potassium permanganate